Some four-wheel vehicles are capable of being selectively switched from a condition of two-wheel drive (often referred to as "4.times.2") to a condition of four-wheel drive (often referred to as "4.times.4"). Such a vehicle requires that one of the axles comprise a set of half shafts in which a hub is locked to the half shaft and receiving drive torque part of the time, but the hub may be rotationally disengaged from the half shaft at other times, during which the hubs are able to freewheel. This is desirable as it prevents forced rotation of the drive train as a result of the front wheels being driven as the vehicle is propelled.
In a vehicle having two axles with four wheels, only one of the axles will be provided with steerable wheels. This axle is usually the axle which receives drive torque on a selective basis, the non-steerable axle normally being provided with full-time drive torque. While the technical requirements for a non-steerable, full-time-drive axle are among the least complex of the possible configurations, the combination of steerability in a selective drive axle provides the greatest amount of technical challenge. For that reason, among others, it is highly desirable to be able to combine and simplify structures to the fullest extent possible.
There are several devices shown in the prior art disclosing mechanisms for rotationally engaging and disengaging a hub. Many of these devices disclose locking hub clutch systems that have a separate vacuum or pressure chamber located at the outer end of the wheel hub. The problem with these devices is that they must be attached or integrated into areas where there is little room. This may result in many other problems, such as unsightly protrusions extending from the center of the wheel. One prior art device discloses a hub locking clutch device in which the locking actuator piston operates in a machined cylinder within the axle stub shaft and the axle joint yoke. In this device the cylinder and the locking actuator piston are an integral part of the axle shaft. While this device does not require attachment of a separate vacuum or pressure chamber, like the wheel end devices, the space available in the axle provides a relatively small diameter available for transmitting torque between its elements, resulting in higher stresses on its members.
In yet another device, the hub locking actuator is a hydraulically actuated ring and diaphragm which is attached to the knuckle. While this device has a much larger diameter available for transferring torque than the previous devices, it still requires the addition of a separate pressure chamber.
It is therefore an advantage of the present invention to provide a simplified version of a hub locking actuator device which is formed as an integral part of the knuckle.